1. Technical Field
The present invention relates to a directional display device capable of simultaneously displaying different images in every viewing direction when viewed from a plurality of directions, such as a two-screen display device or a 3D display device (a stereoscopic display device).
2. Related Art
A directional display device such as a 3D display device realizes display of different images (hereinafter, referred to as “directional display”) in viewing directions by providing an image splitter such as a parallax barrier, a lenticular lens or an optical filter in front of a display panel for displaying an image, such as a liquid crystal panel and restricting emission directions of image light rays representing images. For example, JP-A-2005-181668 describes a directional display device using a parallax barrier and JP-A-8-331605 describes a directional display device using an optical filter.
In a directional display device as the known 3D display device, only when longitudinal and lateral directions of an image display surface of a display panel are arranged in a predetermined direction (hereinafter, referred to as a “reference direction” or a “vertical direction”), display of a 3D image (a three-dimensional image or a stereoscopic image) is possible and, when the longitudinal and lateral directions of the image display surface are arranged in an inverted direction (a direction rotated by 90 degrees, hereinafter, referred to as a “lateral direction”) of the longitudinal direction arrangement, the display of the 3D image is impossible. In a directional display device as the known two-screen display device, separation of two screens in the longitudinal direction and the lateral direction is possible. However, there is a problem that a separation direction becomes a horizontal direction (lateral direction) in the longitudinal direction and becomes a vertical direction (longitudinal direction) in the lateral direction.
There is a need for a directional display device capable of simultaneously displaying different images in every viewing direction when viewed from a plurality of direction, similar to the case of the longitudinal direction, even in lateral direction arrangement as well as longitudinal direction arrangement.
For example, JP-A-2006-337496 and JP-A-2006-337844 disclose directional display devices which solve the above problem by a combination of a first polarization control unit and a second polarization control unit which is provided in front of the first polarization control unit. However, in the directional display devices disclosed in JP-A-2006-337496 and JP-A-2006-337844, since it is difficult to provide a pattern of a polarization control area of the second polarization control unit with high precision with respect to a pattern of a polarization control area of the first polarization control unit, separation capability of a plurality of images in the lateral direction arrangement is not sufficient.